1. Field of the Invention
The present invention is directed to a valve timing control device and in particular to a valve timing control device for controlling an angular phase difference between a crank shaft and a cam shaft of an internal combustion engine.
2. Prior Art
Japanese Utility Model Laid-open Print No. Hei.9-280019 published on Sep. 28, 1997 without examination discloses a conventional valve timing control device. This valve timing control device includes a rotational member rotating together with a cam shaft of an internal combustion engine, a rotation transmission member rotating together with a crank shaft of the internal combustion engine and connected to the rotational member so as to be rotated relative to the rotational member, a plurality of vanes extending into plural concave portions, respectively, in such manner that each vane defines an advancing angle chamber and a retarding angle chamber in the corresponding concave portion, a cylinder fixedly fitted in an inner bore of the rotational member, and a control valve fitted movably in axial direction in a bore of the cylinder and controlling the amount of fluid from a fluid source to both the advancing and retarding angle chambers by being driven by an electromagnetic mechanism secured to the internal combustion engine.
If the control valve if moved in one direction (the other direction) with manipulation of the electromagnetic mechanism, a fluid supply to the advancing chamber and a fluid drain from the retarding chamber are established concurrently (a fluid drain from the advancing chamber and a fluid supply to the retarding chamber are established concurrently), which causes concurrent rotations of the rotational member and the rotation transmission member in one direction (the other direction), an angular phase of the crank shaft is advanced (retarded) relative to an angular phase of the cam shaft. Thus, the timing of a valve connected to the cam shaft becomes more advanced (retarded).
However, in the foregoing structure, a first connecting member is required to connect between the rotational member and the cam shaft. In addition, a second connecting member is essential for the connection between the inner bore of the rotational member and the cylinder accommodating therein the control valve. Such first connecting member and second connecting member cause an increase of the number of parts which results in an increase of the production cost of the valve timing control device in addition to the fact that the members act as barriers against an easy and quick assembly of the valve timing control device.
Moreover, in the foregoing structure, when the valve timing control device is fixed to the internal combustion engine, axial movement of the control valve has to be adjusted in such a manner that a distal end portion of the control valve which extends toward the electromagnetic mechanism has to be coupled with a movable member in screw manner which is formed of magnetic material. Such an engagement multiplies the complexity of the assembly of the device.
Accordingly, a need exists for a valve timing control device without the foregoing drawbacks.